An International Olympic Committee executive who played a central role in Los Angeles’ preparation for the 2028 Summer Games has died of a heart attack.

Patrick Baumann, 51, of Switzerland, succumbed while attending the Youth Olympic Games in Buenos Aires.

“This is a great shock which has hit us all very hard,” IOC President Thomas Bach said. “We can hardly believe this terrible news.”

Baumann, who was considered a candidate to one day replace Bach as the leader of the Olympic movement, also served as the secretary general for FIBA, the international body that governs basketball.

An IOC member since 2007, he most recently led a coordination commission overseeing the 2028 Olympics and visited Southern California in August to tour several venues.

“That is particularly extraordinary,” he told The Times after seeing the Rams stadium under construction. “It’s going to be a fantastic scene for sports.”

LA 2028 chairman Casey Wasserman called Baumann “an advocate for the Los Angeles Games who brought dynamic thinking, bold support and passion to the Olympic movement. Patrick was a partner and a friend.”

The IOC announced that it will hold a memorial at the Youth Games in Argentina and fly its flag at half-mast for the next three days.

“We have seen him working hard, as we always knew him, for the sport he loved,” Bach said. “We lose a young and sympathetic leader full of hope who was standing for the future of sport.”